1. Field of the Invention
The present invention relates to an image recognition technique, more particularly to an image area extract unit for extracting a characteristic portion from an image.
2. Related Art
It is proposed that a characteristic portion is extracted from an image of a vehicle, a traffic sign, an advertising display, a person or the like utilizing image recognition. JP-A-2000-22929 proposes a technique for extracting the face area from an image of a person in a person image processing unit. This technique extracts the face area by determining whether the RGB values of each pixel satisfy predetermined fixed criteria for flesh color.
However, the color of the face area in the image (i.e., the RGB values of pixels belonging to the face area) may vary depending on a condition under which the image is taken. Therefore it is difficult to set the fixed criteria for flesh color appropriately. That is, it is every possibility that the technique cannot extract the face area properly depending on a condition under which the image is taken.
Accordingly, in order to extract the face area properly, the criteria for flesh color should be adjusted according to a condition under which the image is taken. However, it is practically impossible to set different criteria for all possible conditions.